


Ki Oni Matsu

by PokieMech



Category: Ao Oni, おそ松さん | Osomatsu-san (Anime)
Genre: Blood and Gore, Demons, Gen, Gore, INCEST FREE, No Incest, No blmatsu, Other Additional Tags to Be Added, Plague, Survival Horror, probably wont finish this story though, tags will update as the story goes
Language: English
Status: Completed
Published: 2016-05-31
Updated: 2016-05-31
Packaged: 2018-07-11 09:11:23
Rating: Teen And Up Audiences
Warnings: Graphic Depictions Of Violence, Major Character Death
Chapters: 1
Words: 4,174
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/7041994
Author URL: https://archiveofourown.org/users/PokieMech/pseuds/PokieMech
Summary: <blockquote class="userstuff">
              <p>5 Brothers catch word of old rumours about an abandoned mansion<br/>in the depths of the villages nearby forest </p><p>They say a monster lives there.</p><p>(an Ao Oni & Osomatsu-san fanfiction. beware the shittyness)</p>
            </blockquote>





	Ki Oni Matsu

**Author's Note:**

> It was the middle of the night when suddenly the idea for this popped into my head. I had to get it out as quickly as possible. I loved playing Ao Oni when I was a younger teen and I also love evilrabbit's Osomatsu fic: 'The Gauntlet'. it made me realise how much I want MORE horrorMatsu rather then rom-com insert-readers and light-hearted angstyMatsu.  
> enjoy this horribly written 1st chapter  
> THIS FIC IS BASED OF THE 6.23 VERSION OF AO ONI but I have tried to change the plot up a little so it doesn't seem too much like copying. I hope it's ok
> 
>  **!!edit!!**  
>  fixed some spelling mistakes and swapped/added/removed some sentences/paragraphs

They had heard rumours about a mansion in the depths of the villages nearby forest  
They say a monster lives there.

 

“This is stupid” Choromatsu scoffed as he and his 4 other brothers trekked up through the muddy forest. “Why did you have to pull us along on some stupid Halloween treasure-hunt trip when Halloween is months away in a mansion that probably doesn’t exist!” 

“So you’re giving up then?” Osomatsu grinned “N-no I’m still going!” he stuttered back “but only because I can’t leave you guys alone for a second! Mum will blame ME if anything happens to you because I’m the only one with any common sense in this household!”

“Just admit it Alex-Fapper-Bell, you wanted to check out this place too~ you made most of the preparations!” he teased, running a finger under his nose.  
“WHO IS ALEX-FAPPER-BELL!?”

“YOU’RE the only one?! Am I the only person in this group that thought this was a bad idea from the start!? If we don’t turn back now we won’t get home before dark!” the 6th born: Todomatsu whined, he’d been tugging at Karamatsu’s arm for the past hour trying to get everyone to turn back. But Totty rarely even pulled his own weight and Kara was now the strongest of their group, so it was more like Todo was getting dragged along. Luckily Karamatsu was the only brother that could tolerate his childish behaviour for so long without wanting to punch him. In fact he seemed almost oblivious to how annoying it was.  
“Tch…. then why did you come with us in the first place?” Ichimatsu mumbled  
“Oh Ichimatsu, did you forget our fabled youngest brother still fears the dark~? To sleep on his own whilst the rest of us are out having such a wonderful bonding experience with Mother Nature? Surly he would feel alone and left ou-” “Didn’t forget, just don’t care” he interrupted

 

The 5 brothers, or should we say: Quintuplets. Osomatsu, Karamatsu, Choromatsu, Ichimatsu and Todomatsu had picked up on old forgotten rumours that spread out across their village a few years ago. Something about someone finding an abandoned mansion. However the rumour was short lived at the time as a strange … almost paranormal occurrence began to transpire shortly afterwards. People began having rather strange nightmares, sleep paralysis, seizures, spontaneous vomiting and random fits of pain.  
In the end only a few people actually caught this strange disease, but all ended up developing some sort of synced schizophrenia, rambling about monsters and things everyone else couldn’t see. The doctors struggled to find a solution, they sought help from nearby villages but were declined in fear of the disease spreading. At one point the priest had attempted an exorcism by request from a desperate mother but it changed nothing.  
Then after 3 months: one by one they just ... dropped like flies. Some were put out of their misery by doctors, some died from latter mentioned symptoms like exhaustion or choking on their vomit and some went missing ... unfortunately there was plenty of evidence to suggest they had attempted a successful mass-suicide or where mauled by the feral dogs or wolves. Sadly to the village this turn of events couldn’t have come sooner. No one wanted to see their loved ones in pain for so long, trapped in a horrifying abyss of pain and fear with no way to ask for help. 

That was more than 3 years ago though, thankfully nothing similar had happened since the ‘madman-plague’. It had left a traumatizing scar on the village, especially the Matsunos, but with time the wound felt like it had begun to close, they were a strong community.

Five of the brothers where now in their early 20s and still living with their parents (who honestly didn’t mind) and on a rainy night, drunk and stuffed to the brim with boredom while flipping through random text in dusty books, Osomatsu had shouted “who wants to go on a treasure hunt?!”  
When Osomatsu mentioned finding abandoned valuables they could sell for all the money they could ever want, they’d all immediately signed up. And that’s what had led them to 2 weeks of preparing and 3 hours trekking through forest on a clear evening. But it had started to go foggy now and some were beginning to have doubts.  
“Oi! Do you see that?” Osomatsu suddenly piped up

“See what?!” Todomatsu jumped. “Over there! Past those trees” he pointed at something in the distance before jogging through a clump of bushes. 

“Stop going off the trail Osomatsu-niisan!” Choromatsu barked. Too late, he was gone. Choromatsu huffed, pinching the bridge of his nose, “... i am honestly going to turn back the next time he does this.... alright ... who wants to get him this time?”

“Kusomatsu can go” 

“b-but I followed him last time! And the time before that! Shouldn’t we be taking turns at this?” 

 

“OOoooiii! Get up here!” Osomatsu shouted from afar “check this out!” They all looked at each other in silence. he'd probably found another dead squirrel or something. But years of such a commanding voice leading them into battles of mischief and adventure where not about to die down now. they simultaneously decided to follow without even thinking, Todomatsu reluctantly being dragged behind.  
They found Osomatsu had climbed up the old remains of a small landslide from the side of one of the many mountains that stuck out in the forest. He waved down at them with a large grin plastered across his face “i found it! I think I found it!” and with that the rest of the brothers scrambled up to meet him. But what was set out before them was … kind of the opposite of what they we’re expecting. The uneven terrain of the forest began to level out up towards a stone manor. It was huge! Maybe 4-5 floors (presuming it had an attic or something) the first floors set of windows where bared like prison cells and the walls where made completely from white stone with a red tiled roof … it didn’t look abandoned at all. They had been expecting a more … old and rickety castle of some sort, sure there where thick vines clinging around the entire house, that proved it had been here for a long time at least. But the grass was finally cut, there were no smashed windows, no cracks in the walls … just a lot of moss and old bird poop on the tiles. This building didn’t look like it would be falling down any time soon. 

“That can’t be it!” Todomatsu exclaimed, finally feeling brave enough to speak up “it’s too … well there’s probably still some people living in there!” he crossed his arms “it’s too well kept”  
“We must have stumbled on to some rich persons land without knowing” Choromatsu scratched his head admiring the structure. it wasn't like anything they had back at their village. “Check the map again… If this is the 3rd time we’ve gotten lost today I’m throwing Karamatsu off the next cliff I see” Ichimatsu huffed “and then I’ll throw myself”  
Choromatsu stuck his hand in his bag, he pulled out a folded yet crinkled sheet and turned it around a few times, trying to locate where they were. “… no… we’re actually still in the right area, but the house or flat land isn't showing .... maybe it was built after the map was made?” he mumbled confused “but I agree, ... this can’t be it” he folded it back up “c’mon guys. Osomatsu, let’s get back to the trail and-” 

“HHEEYY! THE DOORS OPEN!”  
“AAHH! OSOMATSU-NIISAN!” Choromatsu screamed, dropping his bag

Osomatsu had run down onto the long vertical lawn and reached the wooden door before anyone else could be bothered noticing. Of course he was going to knock, it would be rude to not welcome his new neighbours to the valley! (Maybe they had a hot rich daughter~) but before he could touch the door he noticed it was already open. Weird … maybe they just forgot to close it? He grabbed the door handle and pulled it shut ... but it just slid open again? “Well … I… suppose there’s no need to lock your doors in this isolated place? ... it's not like a robber go to the trouble of coming all the way out here” who WOULD wanna live out here anyway? he thought. the door refused to close but didn't open very much from behind the small gap in the door it was pitch black, at least he thought it was. for a split second ... something caught his eyes from inside the black void. "Eh?" He peeked open the door just a bit more, despite his siblings far away protests. 

“NIISAN GET BACK HERE!” Todomatsu stamped his foot to the ground, “YOU’RE GONNA GET US ARESTED FOR TRESSPASSING! DO YOU KNOW WHAT THAT MEANS?!” Choro added. Karamatsu gulped at the thought. “Hm ... Death Penalty” Ichimatsu almost smirked, glancing at Kara to drink in his worried expression. ah ... this trip was turning out to be more effort than he initially thought, he may act like a depressed adolescent but he wasn't in the mood to die today, he still had to feed the street cats back home. But Osomatsu had stopped paying attention, his back facing them while he observed the entrance. then he dropped his own backpack. they stopped shouting to him as they watched it slowly slide from his shoulders and hit the ground. he had abruptly froze in place for a second ... like he had realized something?. he opened the door wider then, but they couldn't see what was in front of him from so far away. The next thing they knew he slammed the door open with a BANG and ran inside, disappearing into the dark hall.

“WHAT ARE YOU DOING?! YOU’RE GOING TO GET US IN TROUBLE!” Choromatsu broke into a sprint across the long lawn “B-Brother! You can’t just enter someone’s house like that!” Karamatsu shouted following after him. with the 3 older brothers gone -2 dashing to the house- Todomatsu panicked and ran after them. Ichimatsu groaned and hesitantly jogging behind him.

 

They ran across the field -not as fast as usual because they had been hiking for hours- but the lawn was rather flat and soft on their boots as it led slightly up towards the entrance of the mansion, the door started to close and Choromatsu ran faster in fear of locking themselves out. he braced himself and rammed the door open with another BANG as it hit the wall again, true to Oso’s word it was unlocked though, and he ended up falling face first on the cold floor when he barged through. Karamatsu stumbled into the room next and quickly went to help him up, closely followed by Todomatsu and after a few breath catches Ichimatsu finally joined. They subconsciously regrouped, moving closer together, the only light source to give them direction was the sun’s rays outside -horribly dimmed by the fog though- in the small doorway, listening for any signs of their oldest brother. “where ... where is he?” Ichimatsu whispered after everyone had stopped huffing “h-hello?! Is anyone here?” Choro called out. To their displeasure the only thing that answered back was his echo. It must have been a large room “Niisan where are you?” Todomatsu called out a bit quieter.  
“That idiot, why’d he run off like that? People might think we’re robbing their house!” Choromatsu mumbled. “Well it’s a good thing it looks like no one’s home then, hey?” Ichimatsu retorted. “He moved kind of urgently though ... wonder what that was about”. “He can’t have gone too far? There’s gotta be a light switch somewhere” Karamatsu mumbled adjusting his eyes and moving to the side. The other 3 followed. He brushed his hand along the black of the painted wall and felt for a switch. Nothing but Wallpaper …. Wallpaper …. Wallpaper ….. wallpaper …. –fabric?! ****

BOOOEEEHHH!!

Karamatsu's hand jerked back, the second he touched it the fabrics red shadow jumped out and the front door slammed shut.

Osomatsu pushed away from the wall, hands raised menacingly as he roared. Causing a shriek from Kara and Choro, a scream from todo, landing on his backside and Ichimatsu hissed, cat ears poking out of his hair in defence. Of course … the eldest was going to riel them up and scare them.  
“What the hell was that for?!” Choromatsu cried as he tried to hit Osomatsu “You stupid eldest brother! I could have died!” Todo joined in. “You should have seen your faces ahaha-UGH!” He burst out laughing at their reaction but was met with a furry fist to the face. “UGH calm down! c’mon I was kidding!” he barked back. He swore for a moment Ichimatsu given him a ... confused look of absolute disgust, but that could have just been the dim lighting. “well … kidding about the scare thingy, that is!" he laughed "I recon this really might be the place we’ve been looking for!” he rubbed his nose again 

“DON’T CHANGE THE SUBJECT!” they all yelled in sync

“No I’m serious! Look! It’s a mansion in the middle of nowhere! And no one’s here! It’s gotta be the place! You said it yourself Choromatsu we’re in the right area!” he exclaimed. But Choromatsu shook his head “There’s bound to be more than one mansion in this place Osomatsu! This forest is huge after all”  
“But look at all the dirt!”  
“What dirt?!” he snapped  
“The dirt all over your face fappymatsu, that you just face-planted in!” he pointed “eh?” Choromatsu touched his cheek, feeling a faint layer of dust brush off, He was right?  
“Found it!” Karamatsu suddenly called out, he flicked something on a nearby wall and the area slowly lit itself to reveal a large entrance room, hallways to their left and right and another door opposite the front door that stood next to a set of stairs. he glanced around the room only to find most of it was covered in a faint layer of dust or cobwebs but it was quite a large space and ... very grand, causing a few “Ooo!’s” from the brothers.  
“It’s a lot prettier on the inside” Karamatsu smiled. Todomatsu wrinkled his nose though “what person wouldn’t clean such an expensive house? If I lived here It’d be spotless” he stated is a rather curious tone, he shivered a little “bbrrrhh~… is it just me or is it cold in here”  
“Exactly!” Osomatsu added “if it’s not clean then no one’s here! It’s totally abandoned!” he rested his hands on his hips. “It’s probably haunted too! Remember that one book that had a funky looking ogre in it?” “That logic doesn’t make any sense, you idiot” Choromatsu groaned “there’s no way monsters could exist, its scientifically impossible-“  
“... Oi” Ichimatsu mumbled awkwardly, getting the others attention. “... Let … Let’s just get out of here … I don’t feel too good” he avoided their stares, trying not to look too uncomfortable by looking at the ground  
There was silence for a minute. Then Osomatsu laughed “what? You scared Ichimatsu?” earning Oso a much more intense glare then he usually got from the 4th born.  
“Osomatsu! Whether our dear younger brother is feeling scared or sick, we should take his feelings into account! Besides! … It is getting pretty late, it may be best to head back soon” Karamatsu went to pat his brother’s shoulder but received a hiss instead “die Kusomatsu!”  
“Oh I see! When I’m scared it’s funny, but when Ichimatsu’s scared we all have to take it seriously!” Todomatsu tapped his foot “t-that’s not what I meant at all Totty!” Kara exclaimed apologetically.

Choromatsu sighed “seriously though …. This IS kind of turning out to be more trouble than we planned…. I suppose we should start to turn back” he headed back towards the front door. A look of relief spread across Todomatsus face ... and surprisingly Ichimatsus face.  
“But we just got here!” Osomatsu whined “don’t you want to look around?!”  
“I wanted to look around an abandoned building full of free spoils to sell and never have to work another day of my life again! Not steal some unsuspecting aristocrat’s valuables and either get hanged for thieving or go to jail where I am guaranteed to spend the rest of my life sentence with you 4!” he grabbed the door knob and turned it a few times, only making it click... no luck?. He turned it again…. And again …. And again?!  
Choromatsu huffed and tried yanked at the door knob, it wouldn’t open. 

“Open it already” the 4th born groaned  
“Mm! I’m trying! Ugh … Its not …. Umf!” He heaved again.  
“ppfft flimsymatsu” he heard Osomatsu muter  
“Heh! Brother, let me try” Karamatsu announced, reluctantly Choro stepped aside for him. Kara twisted the knob a few times but the door didn’t budge. “Hheeeh!” He put one hand on the wall beside and pulled at the handle…. Nothing…. “Out of the way!” Ichimatsu hissed shoving Karamatsu to the side. He tugged at the door next but it didn’t even bend.  
“It’s shut tight …. Osomatsu-niisan did you lock us in!?”  
“What!? Do I look like I have a key?!”  
“You said this thing was open!”  
“It WAS! I even tried to shut it before! but it opened again!”  
“God damn it Osomatsu-niisan! Why’d you have to barge in here in the first place?!”  
Osomatsu stilled at that questioned “Because I thought! …" he looked back towards the stairs , his agitated expression suddenly replaced with confusion "... i-I thought I … saw-?!” 

**SMASH!**

Todomatsu let out another shriek and covered his mouth, the sound of glass smashing suddenly echoed through the room. They all flinched waiting for the noise to vanish. no one stirred an inch as if any movement would draw the cause of the sound closer…. Karamatsu, Choromatsu, Ichi and Todo all exchanged glances… it was what they feared. Someone else must be in the house.  
After a few minutes Osomatsu was the first to move, taking a step towards the now lightened hallway to their right, where the sound had come from.  
“Osomatsu-niisan! Don’t. You. Fucking. dare!” Choromatsu whispered ferociously “It’s probably the owner of the house!” Todomatsu whispered shaking his head desperately  
“Isn’t that a good thing?” he whispered at them casually, no doubt he was taking enjoyment in their petrified forms  
“If they find us we’re dead! We have to get out of here” Choro hissed  
“The doors locked though! And the windows are bared, let’s just ask them for the key and THEN we can get out”  
“DID YOU NOT HEAR WHAT I JUST SAID!?” Choromatsu was practically pulling his hair out as he whispered. Osomatsu just ignored him and walking through the entrance to the long hall “you guys are just being sooks!” he said as he disappeared. The others stood there in awe for a moment, this guy was either really really brave … or really really fucking stupid. Choromatsu gritted his teeth and made the sudden effort to follow in a fit of rage, hoping to get him back before anyone spotted them. The other 3 just watched in silence as he stormed off, not wanting to take part in Choromatsu or the house owner’s wrath. 

 

Osomatsu wandered obliviously down the wide hallway, he passed a door to his left but when he tried to open it it wouldn’t budge, also locked. He continued through the hall to the only other door and barged into what looked like a kitchen-dining room. 2 couches and a large dusty old mat where in a corner down the end or the room, while the kitchen was squeezed into the opposite corner up the other end. An enormous table filled in most of the space in the center of the room with some old white chairs sprawled out around it… its wasn't exactly traditional. who ever build this place might have been of western-origin “excuse me! Sorry to burst in!” he called out. But there was no one in the room. Besides the dust it was rather well kept like the entrance …. Or so he thought as he walked towards the kitchen: Before him was a smashed plate sprawled out on the floor. That explained the source of the crashing sound but… how did it break in the first place? He squatted down in front of the shards. It looked like fine china. “PLEASE FORGIVE US” another shriek came from back in the hallway just as Choromatsu rushed into the room, hands waving frantically as he clapped them into an apology/praying pose “we didn’t mean to enter your home uninvited! The door was open and my stupid brother thought it was-!” he opened his eyes “it was … a-abandoned?” he stuttered looking around  
Osomatsu waved a plate shard in front of him “found your house owner” he smirked  
Choromatsu breathed in relief but quickly recomposed himself, he pointed menacingly at the 1st born “don’t run off like that again! I’m serious! You really will get us in trouble!”  
“when have I EVER gotten you guys into trouble~?” he sneered and stood back up, shoving the shard in his back pocket (it was some pretty old, detailed fine china, he’d have to find out how much it was worth when they got back) “I could name over 100 instances without thinking! Since the day we we’re born you’ve given us nothing but trouble!”  
“Yeah but you guys usually start it! I just follow along~” he laughed  
“Oh honestly” he snorted crossing his arms, at this point he was just too tuckered out to start another fight Oso, what was the point if all his older brother was going to do was taunt every comment he made? The corner of his lips tilted upwards as he sighed in defeat “heh … sometimes … I think YOU’RE the child-like one in this family now” he stared at nothing, waiting for a reaction   
Osomatsu paused for a minute as if considering his words, before giving a light-hearted chuckle as he stared at the ceiling “yeah… we’re all just as child-like as each other… none of us could compete with 'him' though …” he smiled. Choromatsu hummed softly in reply, sticking his hands in his hoodie pocket. rage happily forgotten, a comfortable silence followed for a while as they stood there in the vacant room.

“c’mon … Let’s get back to the others, see if we can get that door open ... At least THEY have the brainpower to stay put” he retorted. Osomatsu bumped his shoulder as they began walking back down the hallway “You are so mean to me today! What have you got against Onii-Chan?” he teased swinging his arm around his shoulder, but choro just pushed him away, trying to hide a smile.  
“gee I don’t know” Choromatsu began counting his fingers “for somehow convincing us to come along on this wild goose chase? For dragging us off the road 6 times and getting us lost twice-no THREE times today? For locking us in this empty manor possibly with no way out??”  
“ahh you worry too much Alex-Fa-“ “DON’T finish that sentence, I am NOT in the mood!”  
“heheh … eh? Where’d they go?” Osomatsu abruptly stopped at the end of the hallway

Choromatsu turned his head from Oso to look at the lit entrance room. Karamatsu, Ichimatsu and Todomatsu had all vanished. After a second of confusion he clicked his fingers “oh! Maybe they opened the door!” he ran over to the exit and turned the knob again  
…..  
Nope, still locked. “Oh come on!” he cried hammering his fist against the stern wooden structure. Osomatsu made a raspberry sound “ppfft! Their probably gonna jump out … Oooh sooo funny! Trying to scare Onii-Chan are we? LAME!” Osomatsu’s voice echoed through the room “come on out already, it’s not witty after the first time!” he taunted  
No response  
“It’s ok! There’s no one here, it was just a random plate smashed on the ground!” Choromatsu called out “…. Guys?" no response "… K-Karamatsu-Niisan? …Ichimatsu? ... Todomatsu!? This isn’t funny! Come on! we need to find a way out!”  
No response  
Osomatsu looked around the room, were they that angry about getting scared that they’d stoop so low as to try and scare HIM now? Choromatsu joined him in searching the entrance after a while of more silence. Surprisingly the dust wasn’t so thick that they could leave footprints, so there was no way of tracking them. Todomatsu was right, it really was cold in here... Osomatsu was about to speak again when a long creaking sound broke through the silence. Like something heavy was about to break through the flimsy old wooden floorboards. Again the brothers stopped in alarm. Heads turning upwards to the old timber ceiling above. another long creak ... then another .... then another. like some very overweight person was walking on the wooden floor above them. but it was getting fainter as if it was slowly walking away crrrreeeeeeaaak ............. ccrrreeeaaaak ...................... ccrreeaakk .................................. creeaak ........................................................................ 

 

**silence/ ******

****

********

“… What was that?” Choromatsu whispered, neither of them daring to take his eyes off the ceiling.

**Author's Note:**

> I swear there will be less cheesy comedy in any more chapters that are published
> 
> !this hasn't been proof read!  
> !feedback is appreciated! 
> 
> This story was very rush so apologize for any spelling mistakes and random changes of mood in the characters ^^U  
> I honestly don't know if i'll continue this, It may get a second chapter but it wont come out for quite a while, I still have to start the final chapter on my first oso fic.


End file.
